Regulation of heating furnaces



Feb. 7, 1933.

G. A. MERKT REGULATION OF HEATING FURNACES 2 Sheets-Sheet 1 Filed March 4, 1932 llll' E 122mm for Feb. 7, 1933. G. A. MERKT REGULATION OF HEATING FURNACES Filed March 4, 1952 2 Sheets-Sheet 2 combustible mixture of fuel, air and recir- Patented Feb. 7, 1933 cus'mv A. MERKT, or woacn'srma', mssaonusnrrs'assrenon no member 'consrauc- TION 0011mm, orwoaons'rna, sans .massacnusnrrsa conrom'rrou olrj'mssacnnaneuna'non or HEATING summons Application filed Iarcliv4,

The present invention relates in general,

to the regulation or heating furnaces. More particularly, the invention rovides a regulatory system applicable to urnaces wherein resort is had to recirculation of aportion of the combustion products, as disclosed, for example, in my United States Letters Patent No. 1,814,567, dated Julyl i, 1931;

The present invention contemplates automatic regulation, in-a coordinated manner, of the various factors and elements that affect the composition and temperature ofthe culated combustion productsburned in such a furnace. Other and further objects and advantages ofthe inventionwillappear from the following detailed description thereof, taken in connection withftheaccompanying illustrative drawings,- in which a Figs. 1 and 2 are schematic sectional views illustrating different; applications of the principles of my invention to a simple non-. regenerative type of heating furnace.

Like reference characters "refer to like parts in the different figures.

Referring first to Fig. 1', 'Ihave shown in vertical section a heating furnace 1 of simple conventional form, said furnace providing the usualelongated combustion chamber 2, having at one end a fuel port 3 and at the opposite end an exit port 4, through which the products of combustion, after travelling the length. of the chamber 2, are dischargeinto a suitable ofi'take flue. or pas'- sage 5.- 'In order to secure a recirculation,

of aportion of such combustion products through the furnace, an arrangement of drafting apparatus,- similar tothat employed in my aforesaid Patent No. 1,814,567, may be utilizedyto this end, the ofl'take flue or passage 5 is suitably connected, as by a passage 5, with an outwardly opening Venturi tube or duct 6, within'which, in proper relation to the throat thereof, is disposed an upwardly directed nozzle 7, the latter being supplied with air .by an [exterior suitably driven blower '8, whose. intake is indicated at 9. i i

For a purpose to be hereinafter described, the effective discharge area of the air nozzle idles of said wings, larly in unison by the rocking ofanarm i932. Serial K055196377.

7 is made adjustable, as, for example, employment ofpivoted wings 1 0, 1 0 which may be caused to approach each-other for the contraction of the nozzle area, or to recede from each other, for the expansion of the nozzle area by any suitable ad usting means, such as the intermeshing gears 11, 11 secured to thefpi'votal spinand movable angu- 12, alsosecured to-one of said a spindles, Any other means,

well known in the art, maybe employed for increasing or decreasingthe effective discharge area. of the nozzles 7. Also, for. a purpose to be hereinafter de-' scribed, the volume of'airsupplied ,to'the nozzlei7 bythe blower 8 is adjustable or regulable, such, adjustment or regulation being by the secured in anysuitablefmanner as by a pivoteddamper 13 disposed in the inlet 9 of said blower and having an operating arm 14.

Beyond its throat 15, the duct '6 provides -an extension 16 openinglvto the atmosphere for the discharge of a portion of the mixed current of air and Waste furnace gases, said gases, as vwill be well understood, flbein'g entrainedand drawn upwardly in the duct 6 by the air discharged from nozzle 7. A branch flue or passage 17, communicating with the duct 6 in the vicinity of its throat 15, receives that portion of this mixed .cur-

rent of air and, waste furnace gases which does not make exit to the atmosphere through the extension 16; a valve or damper 18, disposed at the juncture of branch 17 with duct 6 is operable by an arm 19 to establish proportionately the volumes of the mixed current of air and waste furnace ases that pass respectively to the atmosp ere (through extension :l6)and to the furnace (through-branch duct 17). In other words, the position of damper 18 determines the amount of the mixture that is diverted to the 'furnace'for recirculation purposes; if only. a small amount isso diverted, then the bulk of said mixture is discharged to the atmosphere through extension 16, while, conversely, ifa large amount is diverted through duct 17, then only a small amount is discharged through extension 16.

The duct 17 conveys the mixture flowing therethrough into the fuel intake end of combustion chamber 2, for supporting the combustion of the fuel that s directed through the intake port 3 from any suitable burner 20. As shown in Fig. 1, the duct 17 may communicate by two branches with the combustion chamber 2, one of these branches 21 providing the primary supply of combustion-supporting mixture that enters with the fuel from burner 20 through the intake port 3, and the other branch 22 providing a secondary supply of combustion-supporting mixture that enters by way of a ort 23. At the juncture of the two branc es 21 and 22 is disposed a valve or damper 24 which is operable by an arm 25 to establish proportionately the volumes of mixture passing, respectively, to the furnace as primary and secondary combustion-supporting supplies,-the position of said damper 24 determining the ratio in which the mixed current is divided between the primary and secondary branches.

As shown in Fig. 1, the furnace interior is equipped with a suitable thermostatic de vice 26, so arranged that variations in temperature within the furnace will produce movements of an arm 27 of said device. The

arm 27 may be provided with suitable connections to some or all of the adjustable or regulable elements hereinbefore described; as shown, a cord or cable 28 may run from said arm to the arm 19 of damper 18, and said arm may have its movements communicated in turn to the arm 12 of the adjustable air nozzle 7, as by means of a connecting link 29 between said arms 19 and 12, which link is adjustable in length by means of a turn-buckle or other equivalent device 36. Also, the movable arm 27 of the thermostatic element 26 may be connected, as by acord or cable 31, with an operating arm 32 for a throttle valve 33 in the fuel supply line that feeds the burner 20, and another cord or cable 34 may connect said arm 27 with the operating arm 25 of valve or damper 24.

With the apparatus arranged and connected up as described above and as shown in Fig. 1, it is evident that any appreciable increase or decrease of the temperature within the furnace, from the temperature desired and for which the thermostatic device 26 has been set, will influence, in appropriate manner and degree, any one or more .of the following factors that have a part in determining the temperature produced in the furnace:the effective area of the air nozzle 7, the setting of the mixture-diverting damper 18, the setting of the mixture-dividing damper 24, and the setting of the fuel supply valve 33. As a result of these automatic adjustments, or any of them, occurring in response to the action of the thermostatic device 26, it is possible to maintain substantially constant the temperature conditions within the combustion chamber 2, and it will be understood also that such regulation of the furnace temperature may be obtained independently of any device such as 26 which is sensitive to temperature, as by the coordination and tying together, in the manner herein disclosed, of some or all of the adjustable or regulable factors that influence the temperature attained in the furnace. For example,

instead of variations in the furnace temperature being made the basis of the coordinated control, as above described, the variations in the amount of fuel admitted to the burner 20 by the throttle valve 33 may be made the basis of the coordinated control; in such a situation, the arm 32 of said valve by suitable connections to the arms 19 and 25 of dampers 18 and 24 respectively would provide by its fuel regulating movements, the necessary movements of said dampers'18 and 24 and of the air nozzle regulating wings 10, 10, such as to increase or decrease the amount of combustion supporting mixture delivered at the ports 3 and 23 in the proper relationto increases or decreases in the amount of fuel supplied, thereby to give the desired furnace temperature.

It will" be noted that the air blast from nozzle 7 in the ejector stack or duct 6 performs the function of creating" the desired furnace draft, and also performs the function of creating the driving pressure in the throat 15 of stack 6 for the recirculation through the furnace of a predetermined part of the resulting mixture of air and waste gases. These functions are in the main dependent upon the nozzle pressure exerted by the blowing device 8. This nozzle pressure may be varied by varying the resistance or load on the blowing device 8, in response to pressure conditions within the system. To this end, the operating arm 14 of damper 13 in the inlet 9 of said blower, may be connected, as by linkage 35, with a diaphragm 36 of a manometer 37, whose interior chamber is in communication, through a pipe 38, with the'ofl'take passage 5' of the furnace. Variations of pressure in said oiftake will therefore be reflected 1 in an increase or a decrease in the amount of air drawn in by the blower 8 and delivered by the nozzle 7.

Fig. 2 depicts a preferred embodiment of the foregoing principles of coordinated regulation and control for furnaces that employ a recirculation of the waste gases. In this embodiment of my invention, the general arrangement of the apparatus is similar to that of Fig. 1, in that the ofltake 5, 5 from the furnace chamber 2 is connected to an ejector stack 6, having'disposed therein the adjust- 1 able air nozzle 7 supplied by a blower 8; also,

which the first, 39, is.=so-located in the chamher 2 as to be responsive to the flame temperature substantially at the point of initial I combustion, while the other, 40-, is so 'located asjto. be .respons'ive to'the lower temperature prevailing-at the end or offtake of the furnace. "chamber; The thermocouple 39 has suitable electrical connections 41 aconftrol device 42 ofconventional,typ e, -the latter beingassociated, electric'ally with asuitable 'actuator43 connected to' the operatmgarm *12,fo"r the adjustable -wings 10, of the nozzle. Z. In-this way; the air nozzle-ejector V t'hro'at ratio 'andfeonsequently, the quality or "composition of: the-mixture formed in the throatf151of ejectorstack 6 is regulated by the a ..'com'bustion' temperature, because the combusflame or combustiontemperature in the furv nace; ifi'sueh'temperature goes too high, the

mixture has its "proportion of air decreased, and this inzturncauses a lowering of the -tiono'f fuel in the furnace is supported by that part' of. such mixturewhich is diverted through the duct or passage 44, correspond{ ing substantia-llyto the duct 17iof Fig-11, .If

the combustion temperature goes too lowfthe mixture automat cally enrlched with air,

therebyproducing. higher combustion temperature inf'the' furnace.

The other thermocouple 40, .which meas ures the end or. final temperature in thefurnace :(fafte the-combustion products have -given .up part of their heat to the articles or materials that are placed in the furnace to'be heated), has suitable electrical connections 45 t0ja control device 46 of conventional' type,- the latter, being associated electrically with a suitable actuator 47 connectedto the operating arm 32 of the throttle valve 33in fuel supplypipe 33 that-feeds the burner 20.

Thus, when the end temperature -'With-in the furnace chamber gets below a predetermined ,deg'ree; more fuelis-admitted through the valve 33,'and when this end temperature gets too highythmsupply of. 'f-uel is c'orrespondg' ingly' reduced "by said; valve. In other words,;

the amount offuel supplied to thebnrner 20 tional to the.;a i nountof heat givenup by the furnace to the articles and 'materialsf that undergo heating .in'the chamber 2. Such automatically-produced variations in the flow offuel-to the burner 20 are made Ito, produce corresponding variations 7 in the amount of -combustionsupporting mixture d vertetlflto the furnace; through the duct or by the draftv vious that.'for-eac lin'said furnace gdiverted;

is regulate'dfso as to bs-substantially roper; r

I a heatingfurnace; an air; blastloperative for a the entrainment and dischargesoff waste jfu-r ,nace gases, means "foradivert'ing allportion of (the mixtureihus formed ofdair and furnace gasesto 'theintak'eof the fu rnace,-to supportj inga restricted a erture 49, and it is ob-. change of variation in the rate of fuel flow produced by movement of valve 33, there will be a change of variation in the differential between the pressures prevailing in pipe 33' on opposite sides of said plate 48. The pressure responsive de- V106 50 has the two chambers on opposite sides of. its diaphragm 51connected, respecgv tively, by pipes 52 and 53-With the pipe 33' -'on opposite sides of said plate. The diaphlegm-51 of device 50 isconnected, as shown at .5-ZLWVltl1 an operating arm 55 for the mixture-diverting damper 18 at the "juncture ofduct 44 with-the throat 1 5 ofejector, stack 6. ltfollowsjthat when the fuel sup ply to burner 20 is increased, the damper 18 will be automatically moved to a position Where more of the mixture from ejector stack 6 is ditert'ed through duct 44,'-and conversely,

when thefnel supply is decreased, the damper 18 will be moved automatically to decrease the, amount of'diverted mixture, with a cor--v respondin g increase in the amount of'mixture exhausted to the atmosphere through the extension .16 of ejector stackuti. f Themixt-ure CllVGItQCl'tO the recirculating duct44 is preftuous passage'through thesame, a portion of the heat contained in the'w-astegases fioW- mg through the otftake pasagesv 5-and 5' of 'the fl1rnace, said exchanger or recuperator 1' 56 p'rovrdmg the conventional tube/s57, 57 for theflow of-sai'd waste gases. 'Thus'the-diverted combustion-supporting mixture, which ultimately is delivered to the fuel port 3 of the fuel supplied by burner 20.

V 1. Ina Waste gasrccirciilating system for a heating furnace,'an ai'r'blast operative for the entrainment and discharge of wastefu'rerably conveyed thereby to aheat'exchanger or recuperator 56, there to absorb, in its tornace-gases," means for diverting a portion of the mixture thus'formed'of 'airandfifurnac'e gases to the intake of' the furnace, to support a combustion of the. fuel used" insaid furnace,

andinean's for regulatin-g'bythe temperature I theamountyof said mixture so a a2, In a waste system for combusiion of the' fuel-used said furnace, and means responsive to temperature-chm es v ,u'ith-in the furnace for varyingithe ratio e5 passage 44' from 'thege'je'ctor stack-6, inxthea' following maiirierrfAt 'a' point inthe fuel supply pipe 33 before 'the throttle {valve '33 I is reached said pi'pe provides a plate 48, h'avrted porthe entrainment and discharge of waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake of the furnace, to support combustion of the fuel used in said furnace, and means for re ulating by the temperature in said furnace t I e composition of said mixture.

4. In a waste gas recirculating system for a heating furnace, an air blast operative for the entrainment and discharge of waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake of the furnace, to support combustion of the fuel used in said furnace,

and means responsive to temperature changes within the furnace for changing the proportions of the ingredients of said mixture.

5. In a waste gas recirculating system for a heating; furnace, an air blast operative for the entrainment and discharge of Waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake of the furnace, to support combustion of the fuel used in said furnace, and means for regulating by the temperature in said furnace the amount of fuel used in said furnace.

6. In a waste gas recirculating system for a heating furnace, an air blast operative for the entrainment and discharge of waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake of the furnace, to support combustion of thefuel used in said furnace,

' and means responsive to temperature changes within the furnace for varying the amount of fuel used in said furnace.

7. In a waste gas recirculating system for a heating furnace, an air blast operative for the entrainment and discharge of waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake of the furnace, to support combustion of the fuel used in said furnace, and means for regulating by the temperature in sai furnace the amount of said mixture so diverted andthe amount of fuel burned in the furnace with said mixture.

8. In a waste gas recirculating system for a heating furnace, an air blast o erative for the entrainment and discharge 0 waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake ,of the furnace, to support combustion of the fuel used in said furnace, and

means responsive to temperature changes within the furnace for varying the ratio be tween the discharged and the diverted portions of said mixture, and for varying the amount of fuel burnedin said furnace with the diverted portion of said mixture.

-9.- In a waste gas recirculating system for a heating furnace, an air blast operative for the entrainment and discharge of waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake of the furnace, to support combustion of the fuel used in said furnace, and means for regulating by the temperature in said furnace the composition of said mixture and the amount of fuel burned in said furnace with the diverted portion of said mixture.

10. In a waste gas recirculatng system for a'heating furnace, an air blast operative for the entrainment and discharge of waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake of the furnace, to support combustion of the fuel used in said furnace, and means responsive to temperature changes within the furnace for changing the proportions of the ingredients of said mixture and for varying the amount of fuel burned in the furnace with the diverted portion of said mixture.

11. In a waste gas recirculating system for a heating furnace, an air blast operative for the entrainment and discharge of waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake of the furnace, to support combustion of the fuel used in said furnace, and means for regulating, coordinately, the amount of said mixture so diverted and the amount of fuel burned in said furnace.

12. In a waste gas recirculating system for a heating furnace, an air blast operative for the entrainment and discharge of waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake of the furnace, to support combustion of the fuel used in said furnace, and means for regulating, coordinately, the composition of said mixture and the amount of fuel burned in said furnace.

13. In a waste gas recirculating system for a heating furnace, an air blast operative for the entrainment and discharge of waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake of the furnace, to support combustion of the fuel used in said furnace, and means for regulating, coordinately, the composition of said mixture, the amount of the same so diverted, and the amount of fuel burned in said furnace.

14. In a waste gas recirculating system for a heating furnace, an air blast operative for the entrainment and discharge of waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake of the furnace, to support combustion of the fuel used in said furnace. and means for regulating by the combustion or flame temperature in said furnace the composition of said mixture,

15. In a waste gas recirculating system for a heating furnace, an air blast operative for the entrainment and discharge of waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake of the furnace, to support combustion of the fuel used in said furnace, and means for regulating by the end temperature in said furnace the amount of fuel used in said furnace.

16. In a waste gas recirculating system for a heating furnace, an air blast operative for the entrainment and discharge of waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake of the furnace, to support combustion of the fuel used in said furnace, means for regulating by the combustion or flame temperature in said furnace the composition of said mixture, and means for regulating by the end temperature in said. furnace the amount of fuel used in said furnace.

. 17. In a waste gas recirculating system for a heating furnace, an air blast operative for the entrainment and discharge of waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake of the furnace, to support combustion of the fuel used in said furnace, and means for regulating by the end temperature of said furnace the amount of fuel used therein and the amount of said mixture so diverted.

18. In a waste gas recirculating system for a heating furnace, an air blast operative for the entrainment and discharge of waste furnace gases, means for diverting a portion of the mixture thus formed of air and furnace gases to the intake of the furnace, to support combustion of the fuel used in said furnace, means for regulating by the combustion or flame temperature in said furnace the composition of said mixture, and means for regulating by the end temperature in said furnace the amount of fuel used in said furnace and the amount of said mixture so diverted 19. In the operation of a heating furnace, the improvement which consists in entraining the waste furnace gases by a blast of air on the outgoing side of the furnace, diverting a portion of the resulting mixture of air and waste gases to the ingoing side of the furnace to support combustiontherein, and regulating, coordinately, the amount of mixture so diverted and the amount of fuel used in said furnace.

20. In the operation of a heating furnace, the improvement which consists in entraining the waste furnace gases by a blast of air on the outgoing side of the furnace, diverting a portion of the resulting mixture of air and waste gases to the in going side of the furnace to support combustion therein, and regulating, coordinately, the composition of said mixture and the amount of fuel used in said furnace.

21. In the operation of a heating furnace, the improvement which consists in entraining the waste furnace gases by a blast of air on the outgoing side of the furnace, diverting a portion of the resulting mixture of air and waste gases to the ingoing side of the furnace to support combustion therein, and reg ulating, coordinately, the composition of said mixture,the amount of the same so diverted, and the amount of fuel used in said furnace.

22. In the operation of a heating furnace, the improvement which consists in entraining the waste furnace gases by a blast of air on the outgoing side of the furnace, diverting a portion of the resulting mixture of air and waste gases to the ingoing side of the furnace to support combustion therein, and regulating by the temperature in said furnace the amount and composition of the mixture "so diverted and the amount of fuel burned in said furnace. 

